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CAS 174672-06-1UNII: 810U6C2DGG

MW 168.3864, MF C7 H6 B Cl O2

Onychomycosis is a disease of the nail caused by yeast, dermatophytes, or other molds, and represents approximately 50% of all nail disorders. Toenail infection accounts for approximately 80% of onychomycosis incidence, while fingernails are affected in about 20% of the cases. Dermatophytes are the most frequent cause of nail plate invasion, particularly in toenail onychomycosis. Onychomycosis caused by a dermatophyte is termed Tinea unguium. Trichophyton rubrum is by far the most frequently isolated dermatophyte, followed by T. mentagrophytes. Distal subungual onychomycosis is the most common presentation of tinea unguium, with the main site of entry through the hyponychium (the thickened epidermis underneath the free distal end of a nail) progressing in time to involve the nail bed and the nail plate. Discoloration, onycholysis, and accumulation of subungual debris and nail plate dystrophy characterize the disease. The disease adversely affects the quality of life of its victims, with subject complaints ranging from unsightly nails and discomfort with footwear, to more serious complications including secondary bacterial infections.

Many methods are known for the treatment of fungal infections, including the oral and topical use of antibiotics (e.g., nystatin and amphotericin B), imidazole anti-fungal agents such as miconazole, clotrimazole, fluconazole, econazole and sulconazole, and non-imidazole fungal agents such as the allylamine derivatives terbinafme and naftifϊne, and the benzylamine butenafine. However, onychomycosis has proven to be resistant to most treatments. Nail fungal infections reside in an area difficult to access by conventional topical treatment and anti-fungal drugs cannot readily penetrate the nail plate to reach the infection sites under the nail. Therefore, onychomycosis has traditionally been treated by oral administration of anti-fungal drugs; however, clearly this is undesirable due to the potential for side effects of such drugs, in particular those caused by the more potent anti-fungal drugs such as itraconazole and ketoconazole. An alternative method of treatment of onychomycosis is by removal of the nail before treating with a topically active anti-fungal agent; such a method of treatment is equally undesirable. Systemic antimycotic agents require prolonged use and have the potential for significant side effects. Topical agents have usually been of little benefit, primarily because of poor penetration of the anti-fungal agents into and through the nail mass.

AN-2718 is a topical benzoxaborole compound that has a high level of nail penetrance [51]. Initial data have suggested that it may be more effective than tavaborole for T. rubrum and T. mentagrophytes[55]. It has recently completed Phase I clinical trials (NCT00781664) [56].

Reduction of 2-bromo-5-chlorobenzoic acid with BH3/THF in THF gives 2-bromo-5-chlorobenzyl alcohol , which is protected as the methoxymethyl derivative by treatment with MOM-Cl in the presence of DIEA in CH2Cl2. Metalation and boronylation of aryl bromide either with t-BuLi or BuLi (1,2,3,4) and (i-PrO)3B (4) or B(OMe)3 in THF affords the title compound .

Alternatively, reaction of 3-chlorobenzaldehyde with p-toluenesulfonylhydrazide in MeOH provides tosyl hydrazone which undergoes thermal decomposition in the presence of BBr3 and catalytic FeCl3 in refluxing CH2Cl2, followed by heating with aqueous NaOH to produce the title oxaborole compound .

Aldrich) in methylated spirits (40 ml) was added slowly at below 10°C to a stirred suspension of p-toluene-sulphonylhydrazide (20.7 parts;

0.108M) in methylated spirits (150 ml). The reaction mass was then stirred at 20 to 25°C for 1 hour and then heated at 60-70°C for 1M hours when the reactants and products dissolved. The solvent was then removed by rotary evaporation and the product was obtained as a solid which was slurried with ether and washed with n-hexane. Yield = 27.2 parts (81.5% theory) mpt 122-3°C. Elemental analysis

A suspension of anhydrous ferric chloride catalyst (0.75 parts, Fisons) in dry dichloromethane (20 ml) was added at 20 to 25°C simultaneously with boron tribromide (25 parts, 0.1M, Aldrich) in dry dichloromethane (100 mis) to a stirred suspension of the hydrazide from a) above (10.18 part, 0.033M) in dry dichloromethane (160 mis) under a nitrogen blanket. The reactants were then stirred under reflux and the evolved hydrogen bromide trapped under aqueous sodium hydroxide. After 3 hours stirring at reflux, the reactants were allowed to stand at 20- 25°C for 48 hours and then stirred under reflux for a further 4 hours. The reaction mass was then cooled and the solvent removed by rotary evaporation. The solid obtained was then stirred under reflux with 2N sodium hydroxide solution (160 ml) for 3 hours. The brown aqueous suspension was extracted with dichloromethane (50 ml), screened and then acidified to about pH 2 by addition of 2N hydrochloric acid. The solid was filtered, slurried with dichloromethane (400 ml) and then washed with a saturated solution of sodium bicarbonate followed by water.

Yield = 24 parts (43% theory). The solid was slurried in hot

dichloromethane and filtered to give 0.36 parts oxaborole mp 140-45°C. The dichloromethane solution was cooled and the solid filtered giving a further 0.35 parts oxaborole mp 146-8°C. The solids were combined and recrystallised from methylated spirits.

A solution of borane-tetrahydrofuran complex in THF (0.15 L, 1.5 eq) was added dropwise to a solution of 2-bromo-5-chlorobenzoic acid (24 g) in anhydrous tetrahydrofuran (0.24 L) at 0°C and under argon atmosphere. The reaction mixture was stirred at room temperature for 16 h, before being slowly poured onto 0.10 L of a 2N aqueous solution of hydrogen chloride at 0°C. The mixture was stirred for 15 minutes and the volatiles were removed under reduced pressure. The aqueous layer was extracted with ethyl acetate and the combined organic layers were washed with a IN aqueous solution of sodium hydroxide and then water. After drying over sodium sulfate, filtration and concentration under reduced pressure, the crude product was purified by column chromatography; 23.2 g; M.p. 79-80 °C.

To a solution of (B) (6.0 g) in anhydrous tetrahydrofuran (120 mL) at -78°C was added dropwise a solution of butyllithium in hexane (15.6 mL, 1.1 eq). To the resulting yellow- brown solution trimethyl borate (2.5 mL, 1.0 eq) was injected in one portion and the cooling bath was removed. The mixture was warmed gradually for 30 minutes. After stirring at room temperature for 2 hours, 8.0 ml of a 6N aqueous solution of hydrogen chloride were added and the reaction mixture was left stirring overnight at room temperature. Evaporation of the volatiles gave a residue which was taken up in ethyl acetate, washed with water, brine, dried over sodium sulfate and then evaporated. The crude product was crystallized from ethyl acetate to give 1.4 g of 5-chloro-l-hydroxy-3H-2,l-benzoxaborole (1) as a white powder. Purification of the filtrate by column chromatography afforded 1.2 g more of 1. M.p. 147- 149 °C.

1-Hydroxy-dihydrobenzoxaboroles, such as Cl, were synthesized as shown in Scheme 1. The protected o-bromobenzyl alcohol derivative (18), prepared from 16 or 17, was converted into the corresponding phenyl boronic acid. Deprotection of the methoxymethyl ether using hydrochloric acid followed by spontaneous cyclization gave the target compounds.

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DR ANTHONY MELVIN CRASTO, Born in Mumbai in 1964 and graduated from Mumbai University, Completed his Ph.D from ICT, 1991,Matunga, Mumbai, India, in Organic Chemistry, The thesis topic was Synthesis of Novel Pyrethroid Analogues, Currently he is working with GLENMARK PHARMACEUTICALS LTD, Research Centre as Principal Scientist, Process Research (bulk actives) at Mahape, Navi Mumbai, India. Total Industry exp 29 plus yrs, Prior to joining Glenmark, he has worked with major multinationals like Hoechst Marion Roussel, now Sanofi, Searle India Ltd, now RPG lifesciences, etc. He has worked with notable scientists like Dr K Nagarajan, Dr Ralph Stapel, Prof S Seshadri etc, He did custom synthesis for major multinationals in his career like BASF, Novartis, Sanofi, etc., He has worked in Discovery, Natural products, Bulk drugs, Generics, Intermediates, Fine chemicals, Neutraceuticals, GMP, Scaleups, etc, he is now helping millions, has 9 million plus hits on Google on all Organic chemistry websites. His friends call him worlddrugtracker. His New Drug Approvals, Green Chemistry International, All about drugs, Eurekamoments, Organic spectroscopy international,
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and implementation them on commercial scale over a 29 year tenure till date Aug 2016, Around 30 plus products in his career. He has good knowledge of IPM, GMP, Regulatory aspects, he has several International patents published worldwide . He has good proficiency in Technology transfer, Spectroscopy, Stereochemistry, Synthesis, Polymorphism etc., He suffered a paralytic stroke/ Acute Transverse mylitis in Dec 2007 and is 90 %Paralysed, He is bound to a wheelchair, this seems to have injected feul in him to help chemists all around the world, he is more active than before and is pushing boundaries, He has 9 million plus hits on Google, 2.5 lakh plus connections on all networking sites, 25 Lakh plus views on dozen plus blogs, He makes himself available to all, contact him on +91 9323115463, email amcrasto@gmail.com, Twitter, @amcrasto , He lives and will die for his family, 90% paralysis cannot kill his soul., Notably he has 13 lakh plus views on New Drug Approvals Blog in 212 countries......https://newdrugapprovals.wordpress.com/ , He appreciates the help he gets from one and all, Friends, Family, Glenmark, Readers, Wellwishers, Doctors, Drug authorities, His Contacts, Physiotherapist, etc

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